Method for cooling optical fiber

ABSTRACT

In one embodiment, an optical fiber cooling system includes a first cooling tube oriented substantially in parallel with and spaced apart from a second cooling tube such that an optical fiber pathway is positioned between the first cooling tube and the second cooling tube. The first cooling tube includes a plurality of cooling fluid outlets positioned along an axial length of the first cooling tube which are oriented to direct a flow of cooling fluid across the optical fiber pathway towards the second cooling tube. The second cooling tube includes a plurality of cooling fluid outlets positioned along an axial length of the second cooling tube which are oriented to direct a flow of cooling fluid across the optical fiber pathway towards the first cooling tube.

CROSS REFERENCE

The present disclosure claims priority to U.S. Provisional Application61/255,527, filed Oct. 28, 2009 and entitled “Systems and Methods forCooling Optical Fiber”.

BACKGROUND

1. Field

The present specification generally relates to systems and methods forproducing optical fiber and, more specifically, to systems and methodsfor cooling optical fiber.

2. Technical Background

Glass optical fiber is generally formed by drawing the optical fiberfrom a preform which is heated to a draw temperature in a draw furnace.After the optical fiber is drawn from the preform, the bare or uncoatedoptical fiber may be susceptible to damage from mechanical contact. Suchdamage may adversely affect both the mechanical and optical propertiesof the optical fiber. Accordingly, to prevent such damage, a coating maybe applied to the optical fiber soon after the optical fiber is drawnfrom the preform. However, if the coating is applied to the heatedoptical fiber (e.g., if the coating is applied to the optical fiberimmediately after the optical fiber is drawn from the preform) theelevated temperature of the optical fiber may reduce the effectivenessof the coating for protecting the optical fiber.

Given that the optical fiber process is vertically constrained, coolingof the optical fiber is generally accomplished over the fixed distance.As such, the optical fiber must be aggressively cooled over a fixeddistance to reach a temperature suitable for application of the coating.Accordingly, the rate at which the optical fiber is cooled may be onerate limiting step in increasing the drawing speed of optical fiber.Further, gases currently used to cool optical fibers, such as heliumgas, may be expensive and may require refrigeration to achieve thenecessary cooling thereby adding to the overall cost of the opticalfiber manufacturing process.

Accordingly, alternative systems and methods for cooling optical fiberare needed.

SUMMARY

According to one embodiment, an optical fiber cooling system includes afirst cooling tube oriented substantially in parallel with and spacedapart from a second cooling tube such that an optical fiber pathway ispositioned between the first cooling tube and the second cooling tube.The first cooling tube comprises a plurality of cooling fluid outletspositioned along an axial length of the first cooling tube. The coolingfluid outlets of the first cooling tube are oriented to direct a flow ofcooling fluid across the optical fiber pathway towards the secondcooling tube. The second cooling tube comprises a plurality of coolingfluid outlets positioned along an axial length of the second coolingtube. The cooling fluid outlets on the second cooling tube are orientedto direct a flow of cooling fluid across the optical fiber pathwaytowards the first cooling tube.

In another embodiment, an optical fiber cooling system includes anoptical fiber cooling tube positioned in and substantially coaxial witha cooling fluid supply plenum. The optical fiber cooling tube generallydefines an optical fiber pathway through the optical fiber coolingsystem and includes a plurality of cooling fluid inlets positioned alongan axial length of the optical fiber cooling tube. The cooling fluidinlets are configured to direct a flow of cooling fluid across theoptical fiber pathway from at least two different directions. At leastone cooling fluid vent may be disposed along the axial length of theoptical fiber cooling tube between first and second ends of the opticalfiber cooling tube. The at least one cooling fluid vent may have a crosssectional area which is larger than a cross sectional area of a coolingfluid inlet. Further, the at least one cooling fluid vent may beoperable to exhaust cooling fluid from the optical fiber cooling tubeand thereby prevent bulk axial flow of cooling fluid through the opticalfiber cooling tube. The at least one cooling fluid vent may be fluidlycoupled to a cooling fluid exhaust plenum positioned within the coolingfluid supply plenum.

In another embodiment, a method for cooling an optical fiber during anoptical fiber drawing operation includes drawing an optical fiber alongan optical fiber pathway positioned between a first cooling tube and asecond cooling tube. Thereafter, a flow of cooling fluid is directedonto the optical fiber through cooling fluid outlets positioned along anaxial length of the first cooling tube and a flow of cooling fluid isdirected onto the optical fiber through cooling fluid outlets positionedalong an axial length of the second cooling tube. The cooling fluid isvented such that bulk axial flow of cooling fluid along the opticalfiber pathway is prevented.

Additional features and advantages of the invention will be set forth inthe detailed description which follows, and in part will be readilyapparent to those skilled in the art from that description or recognizedby practicing the embodiments described herein, including the detaileddescription which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cross section of a system for drawing optical fiberfrom an optical fiber preform according to one or more embodiments shownand described herein;

FIG. 2 depicts a horizontal cross section of an optical fiber coolingsystem according to one or more embodiments shown and described herein;

FIG. 3A depicts one embodiment of a cooling tube of the optical fibercooling system of FIG. 2 according to one or more embodiments shown anddescribed herein;

FIG. 3B depicts another embodiment of a cooling tube of the opticalfiber cooling system of FIG. 2 according to one or more embodimentsshown and described herein;

FIG. 4A depicts one embodiment of a cooling fluid outlet in a coolingtube according to one embodiment shown and described herein;

FIG. 4B depicts another embodiment of a cooling fluid outlet in acooling tube according to one embodiment shown and described herein;

FIG. 5 depicts a cooling fluid outlet according to one embodiment shownand described herein;

FIG. 6 depicts one group of cooling fluid outlets according to oneembodiment shown and described herein;

FIG. 7 depicts the optical fiber cooling system of FIG. 2 showing therelative orientation of groups of cooling fluid outlets on opposingcooling tubes;

FIG. 8 depicts a horizontal cross section of an optical fiber coolingsystem according to one or more embodiments shown and described herein;and

FIG. 9 depicts one embodiment of a cooling fluid inlet in a cooling tubeaccording to one embodiment shown and described herein.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of opticalfiber cooling systems, examples of which are illustrated in theaccompanying drawings. Whenever possible, the same reference numeralswill be used throughout the drawings to refer to the same or like parts.One embodiment of an optical fiber cooling system is generally depictedin FIG. 2. The optical fiber cooling system generally comprises a firstcooling tube and a second cooling tube oriented in parallel with oneanother and spaced apart from one another such that an optical fiberpathway is positioned between the first and second cooling tubes. Eachof the cooling tubes may comprise a plurality of cooling fluid outletswhich are oriented to direct a flow of cooling fluid across the opticalfiber pathway towards the opposing cooling tube. Various embodiments ofthe optical fiber cooling system and systems for drawing optical fiberin which the optical fiber cooling systems are incorporated will bedescribed in further detail herein.

Referring to FIG. 1, one embodiment of a system 100 for producing coatedoptical fiber is illustrated. The system 100 may comprise a draw furnace114 for heating an optical fiber preform 112 such that an optical fiber300 may be drawn from the optical fiber preform 112. The preform 112 maycomprise glass or any material suitable for the manufacture of opticalfibers. The draw furnace 114 may be vertically oriented such thatoptical fiber 300 drawn from the optical fiber preform 112 exits thefurnace along a substantially vertical pathway (i.e., a pathway that issubstantially parallel with the z-direction of the coordinate axesdepicted in FIG. 1).

After the optical fiber 300 exits the draw furnace 114, the diameter ofthe optical fiber 300 and the draw tension applied to the optical fiber300 may be measured using non-contact sensors 118, 120. As shown in FIG.1, after the diameter and tension of the optical fiber 300 are measured,the optical fiber 300 passes through an optical fiber cooling system 200which cools the optical fiber. In general, the optical fiber coolingsystem 200 is spaced apart from the draw furnace 114 by a distance Dsuch that the optical fiber 300 cools at ambient temperatures beforeentering the optical fiber cooling system 200. For example, the distanceD between the draw furnace 114 and the optical fiber cooling system 200a may be sufficient to cool the optical fiber sufficient to cool theoptical fiber from the draw temperature (e.g., from about 1700° C.-2000°C.) to about 1300° C. and, more preferably, to about 1200° C. before theoptical fiber 300 enters the optical fiber cooling system 200.

As the optical fiber 300 travels through the optical fiber coolingsystem 200, the optical fiber is cooled to less than about 80° C. and,more preferably, less than about 60° C. by directing multiple flows ofcooling fluid across the optical fiber pathway over which the opticalfiber 300 is drawn through the optical fiber cooling system 200. Ingeneral, the cooling fluid flows are directed across the optical fiberpathway in a direction which is substantially transverse to the opticalfiber pathway. Moreover, the optical fiber cooling system 200 isconfigured to prevent substantial bulk axial flow of the cooling fluidthrough the optical fiber cooling system 200 in the axial direction(i.e., in a direction which is substantially parallel with thez-direction on the coordinate axes in FIG. 1) which, in turn, improvesthe cooling capacity and cooling efficiency of the optical fiber coolingsystem 200. The phrase “bulk axial flow,” as used herein, refers to theflow of cooling fluid in the axial direction through the optical fibercooling system. Bulk axial flow of cooling fluid through the opticalfiber cooling system may disrupt the transverse flow of cooling fluidacross the optical fiber pathway thereby reducing the ability of theoptical fiber cooling system to cool the optical fiber. In theembodiments of the optical fiber cooling systems described herein, bulkaxial flow of cooling fluid through the optical fiber cooling system isprevented by venting the cooling fluid from the optical fiber coolingsystem along the axial length of the optical fiber cooling system, aswill be described in more detail herein.

Referring now to FIG. 2, one embodiment of an optical fiber coolingsystem 200 a is schematically depicted in horizontal cross section. Thephrase “horizontal cross section,” as used herein, refers to a crosssection through the optical fiber cooling system 200 a in an x-y planeas defined by the coordinate axes shown in FIG. 1. The optical fibercooling system 200 a generally comprises a first cooling tube 202 and asecond cooling tube 204. The first cooling tube 202 and the secondcooling tube 204 are hollow tubes which are substantially parallel withone another and spaced apart from one another such that an optical fiber300 may be drawn between the first cooling tube 202 and the secondcooling tube 204. In the embodiments shown and described herein thefirst cooling tube 202 and the second cooling tube 204 are spaced apartby a distance F which is generally less than about 26.0 millimeters and,more preferably, from about 9.0 millimeters to about 13.0 millimeters.

Accordingly, it should be understood that an optical fiber pathway 208along which an optical fiber 300 may be drawn is positioned between thefirst cooling tube 202 and the second cooling tube 204. In theembodiment of the optical fiber cooling system 200 a shown in FIG. 2,the optical fiber pathway 208 is not enclosed. Instead, the opticalfiber pathway 208 is directly exposed to the ambient pressure,temperature and atmosphere of the manufacturing environment in which theoptical fiber cooling system 200 a is deployed. Accordingly, in thisembodiment, it should be understood that the flow of cooling fluid 210directed across the optical fiber pathway 208 may be vented directly tothe surrounding ambient atmosphere along substantially the entire axiallength of the optical fiber pathway 208 as indicated by the fluid flowegress 212. As described herein, venting the flow of cooling fluid 210along the axial length of the optical fiber cooling system 200 aprevents the bulk axial flow of cooling fluid through the optical fibercooling system.

In an alternative embodiment (not shown), the first cooling tube 202 andthe second cooling tube 204 may be positioned within a fluid containmentenclosure (not shown). The fluid containment enclosure may be fluidlycoupled to a cooling fluid recovery system which facilitates the activecollection and recovery of the cooling fluid emitted by the firstcooling tube 202 and the second cooling tube 204. In order to not impedeor otherwise affect the egress of cooling fluid from the optical fiberpathway 208 (i.e., in order to prevent bulk axial flow of cooling fluidthrough the optical fiber cooling system 200 a), the fluid containmentenclosure may be significantly larger than the first cooling tube 202and the second cooling tube 204. For example, where the first coolingtube 202 and the second cooling tube have diameters of about 25 mm, asdescribed in more detail herein, the fluid containment enclosure may begreater than about 75 mm in diameter.

Referring now to FIGS. 2-7, in the embodiments of the optical fibercooling system 200 a shown and described herein, the first cooling tube202 and the second cooling tube 204 are generally circular in crosssection. Accordingly, in the embodiments shown herein, the first coolingtube 202 and the second cooling tube 204 are substantially cylindrical.The cooling tubes 202, 204 are closed at one end and, on the oppositeend, are fluidly coupled to a supply of cooling fluid. In theembodiments described herein the cooling tubes 202, 204 are formed froma metallic material, such as an aluminum or steel alloy or a similarmaterial, and generally have a wall thickness of less than about 13.0millimeters, more preferably less than about 6.5 millimeters and, mostpreferably, less than about 3.5 millimeters. Further, the inner diameter(i.e., twice the (i.e., twice the radius R) of the cooling tubes 202,204 is preferably less than about 100 mm and, more preferably, less thanor equal to 50 mm. In the embodiments described herein the cooling tubes202, 204 have an axial length L of less than about 6 meters, morepreferably less than about 5 meters and, most preferably, about 4meters. However, it should be understood that the axial length L of thecooling tubes may be larger than 6 meters or shorter than 4 metersdepending on the specific system in which the cooling tubes areemployed.

While the first cooling tube 202 and the second cooling tube 204 havebeen described herein as being circular in cross section, it should beunderstood that the first and second cooling tubes may have differentcross sectional geometries. For example, in alternative embodiments thecooling tubes may be substantially D-shaped or semi-circular and thecooling tubes may be oriented such that the curved surfaces of thecooling tubes are opposed to one another. In other embodiments thecooling tubes may be square or rectangular in cross section or haveanother regular or irregular geometrical shape in cross section.Further, while the first cooling tube 202 and the second cooling tube204 have been described herein as comprising a metallic material, itshould be understood that the cooling tubes may be formed from othermaterials including, without limitation, polymers, ceramics, andcomposite materials.

Still referring to FIGS. 2-7, to facilitate cooling the optical fiber300 with the optical fiber cooling system 200 a, cooling fluid is pumpedinto the cooling tubes 202, 204 with a cooling fluid supply system whichis fluidly coupled to the first cooling tube 202 and the second coolingtube 204 with supply conduits 240. In one embodiment, the cooling fluidsupply system may comprise a compressor or other apparatus for supplyinga flow of pressurized cooling fluid. In another embodiment, the coolingfluid supply system may comprise a fan or other mechanism for directinga flow of cooling fluid into the cooling tubes 202, 204. The coolingfluid exits the cooling tubes 202, 204 through a plurality of coolingfluid outlets 206 which are positioned along the axial length L of thecooling tubes 202. The cooling fluid outlets 206 are oriented such thatthe cooling fluid outlets 206 in the first cooling tube 202 direct aflow of cooling fluid 210 from the first cooling tube 202 across theoptical fiber pathway 208 towards the second cooling tube 204.Similarly, the cooling fluid outlets 206 in the second cooling tube 204are oriented to direct a flow of cooling fluid 210 from the secondcooling tube 204 across the optical fiber pathway 208 towards the firstcooling tube 202.

As depicted in FIG. 5, each cooling fluid outlet 206 is substantiallyrectangular in shape with a width W and a height H at the surface of theouter diameter of the cooling tubes 202, 204. In the embodimentsdescribed herein the cooling fluid outlets 206 are generally oriented onthe cooling tubes 202, 204 such that the height H of the cooling fluidoutlets are generally parallel to the x-y plane in the coordinate systemshown in FIG. 1 while the width W of the cooling fluid outlets 206 isgenerally oriented in the z-direction. In the embodiments describedherein the cooling fluid outlets 206 have a width W of less than about0.5 millimeters, more preferably less than about 0.3 millimeters, andmost preferably, less than about 0.25 millimeters. Further, in theembodiments described herein the cooling fluid outlets 206 have a heightH which is greater than about 2.5 millimeters, more preferably greaterthan about 6.25 millimeters, and most preferably, greater than about 7.5millimeters.

In one embodiment the cooling fluid outlets 206 have substantiallyparallel sidewalls such that the height H of the cooling fluid outletsis substantially the same through the radial thickness of the coolingtube 202, as depicted in FIG. 4A. More specifically, the sidewalls 230,232 are substantially parallel with the x-direction of the coordinatesystem depicted in FIG. 4A and, in turn, parallel with one another.However, in other embodiments, the cooling fluid outlets 206 may taperfrom the inner diameter of the cooling tube to the height H at the outerdiameter of the cooling tube.

For example, as depicted in FIG. 4B, the sidewalls 230, 232 of thecooling fluid outlet 206 are tapered from the inner diameter of thecooling tube to the outer diameter of the cooling tube. Morespecifically, in the embodiment of the cooling tube 202 shown in FIG.4B, the sidewalls of the cooling fluid outlet 206 taper from the innerdiameter of the cooling tube 202 to the outer diameter of the coolingtube 202 with respect to the centerline 233 of the cooling fluid outlet206. In the embodiments shown and describe herein, the sidewalls 230,232 are each oriented at an angle α with respect to the centerline 233of the cooling fluid outlet 206. The angle α may be from about 12.5degrees to about 25 degrees and, more preferably, from about 13.0degrees to about 21 degrees. Accordingly, it should be understood that,in the embodiment shown in FIG. 4A, the cooling fluid outlet 206 tapersto the height H at the outer diameter and as such, the height of thecooling fluid outlet at the inner diameter of the cooling tube isgreater than the height H at the inner diameter. For example, where theheight H of the cooling fluid outlet 206 at the outer diameter of thecooling tube is about 7.62 millimeters and the angle α is 20.3 degrees,the height of the cooling fluid outlet 206 at the inner diameter may beabout cooling fluid outlet 206 at the inner diameter may be about 11.782millimeters.

Where the walls of the cooling fluid outlet 206 are tapered, the firstcooling tube 202 and the second cooling tube 204 may be positioned suchthat the flow of cooling fluid 210 exiting the cooling tubes 202, 204(as shaped by the tapered cooling fluid outlet 206) is focused at thecenterline between the first cooling tube 202 and the second coolingtube 204. In another embodiment, the sidewalls of the cooling fluidoutlet 206 may be tapered such that a flow of cooling fluid 210 passingthrough the cooling fluid outlet is not focused at the center of thecenterline between the first cooling tube 202 and the second coolingtube 204. For example, the sidewalls of the cooling fluid outlets of thefirst cooling tube 202 may be tapered such that the flow of coolingfluid is focused between the centerline and the second cooling tube 204.Similarly, the sidewalls of the cooling fluid outlets of the secondcooling tube 204 may be tapered such that the flow of cooling fluid isfocused between the centerline and the first cooling tube 202.Alternatively, the sidewalls of the cooling fluid outlets of the firstcooling tube 202 may be tapered such that the flow of cooling fluid isfocused between the centerline and the first cooling tube 202.Similarly, the sidewalls of the cooling fluid outlets of the secondcooling tube 204 may be tapered such that the flow of cooling fluid isfocused between the centerline and the second cooling tube 204.

In the embodiment of the cooling tubes 202, 204 illustrated in FIG. 3Athe cooling fluid outlets 206 may be equidistantly spaced along theaxial length L of the cooling tubes 202, 204. Accordingly, in thisembodiment, it should be understood that the spacing between axiallyconsecutive cooling fluid outlets 206 is the same along the axial lengthL of the cooling tube 202, 204. For example, in the embodiment shown inFIG. 3A, the axially consecutive cooling fluid outlets 206 may be spacedapart by less than about 50 millimeters, more preferably by about 25millimeters, and most preferably, by less than about 25 millimeters.

Alternatively, in the embodiment of the cooling tubes 202, 204illustrated in FIG. 3B, the cooling fluid outlets 206 are positioned ingroups 207. In this embodiment, axially consecutive groups 207 ofcooling fluid outlets 206 are equidistantly spaced apart by an amount Galong the axial length L of the cooling tube 202, 204. For example, inone embodiment, the spacing G between axially consecutive groups 207 ofcooling fluid outlets is less than about 75 millimeters, more preferablyless than about 50 millimeters, and more preferably, less than about 40millimeters.

Further, as shown in FIG. 6, axially consecutive cooling fluid outlets206 in each group group 207 of cooling fluid outlets 206 areequidistantly spaced by an amount S. For example, in one embodiment, thespacing S between axially consecutive cooling fluid outlets in eachgroup 207 of cooling fluid outlets 206 is less than about 3 millimeters,more preferably less than about 2 millimeters and, most preferably, lessthan about 1 millimeter. In the embodiment of the group 207 of coolingfluid outlets 206 shown in FIG. 6, each group 207 comprises ten coolingfluid outlets 206. However, it should be understood that each group 207may comprise more or fewer cooling fluid outlets 206.

Irrespective of whether the cooling fluid outlets 206 are groupedtogether in groups 207, as depicted in FIG. 3B, or the cooling fluidoutlets are all equidistantly spaced along the axial length L of thecooling tube, as depicted in FIG. 3A, the cooling fluid outlets 206 ofthe first cooling tube 202 are generally positioned to direct a flow ofcooling fluid 210 from the first cooling tube 202 across the opticalfiber pathway 208 towards the second cooling tube 204. Similarly, thecooling fluid outlets 206 of the second cooling tube 204 are generallypositioned to direct a flow of cooling fluid 210 from the second coolingtube 204 across the optical fiber pathway 208 towards the first coolingtube 202. In the embodiments shown and described herein, the coolingfluid outlets 206 of the first cooling tube 202 and the cooling fluidoutlets 206 of the second cooling tube 204 are not oriented in directopposition to one another. Instead, the cooling fluid outlets 206 of thefirst cooling tube 202 and the cooling fluid outlets 206 of the secondcooling tube 204 are offset from one another along the axial length ofthe optical fiber cooling system 200 a. For example, referring to FIG.7, one embodiment of an optical fiber cooling system 200 a is depictedin which the cooling fluid outlets are positioned in groups along theaxial length of the optical fiber cooling system 200 a. As depicted inFIG. 7, each group 207 of cooling fluid outlets on the second coolingtube 204 is positioned between axially consecutive groups 207 of coolingfluid outlets 206 on the first cooling tube 202. Accordingly, thecooling fluid outlets 206 of the first cooling tube 202 do not directlyoppose the cooling fluid outlets 206 of the second cooling tube 204.

While FIG. 7 shows groups 207 of cooling fluid outlets which are offsetalong the axial length of the optical fiber cooling system 200 a, itshould be understood that individual cooling fluid outlets may also beoffset along the axial length of the optical fiber cooling system 200 a.For example, each cooling fluid outlet on the second cooling tube 204may be positioned between axially consecutive cooling fluid outlets 206on the first cooling tube 202.

Referring now to FIGS. 2 and 7, an optical fiber 300 may enter theoptical fiber cooling cooling system 200 a at fiber inlet 218 such thatthe optical fiber 300 is drawn along the optical fiber pathway 208between the first cooling tube 202 and the second cooling tube 204 andexits the optical fiber cooling system 200 a at fiber outlet 220. As thefiber is drawn over the optical fiber pathway 208, cooling fluid issupplied to the optical fiber cooling tubes 202, 204 via fluid supplyconduits 240. The cooling fluid may comprise an elemental gas, such ashelium or nitrogen, or a mixture of gasses such as, for example, air.Alternatively, the cooling fluid may comprises a combination of variousgasses such as helium, nitrogen and/or carbon dioxide. The cooling fluidmay be chilled or, alternatively, supplied to the optical fiber coolingsystem 200 a at ambient temperatures.

In one embodiment, the cooling fluid may be supplied to the firstcooling tube and the second cooling tube at pressures suitable forachieving a flow of cooling fluid 210 from each cooling fluid outlet 206which has a velocity of less than about 0.95 mach. For example, when thecooling fluid is air, the air may be supplied to the first cooling tubeand the second cooling tube such that the pressure in the first coolingtube and the second cooling tube is about 7 psig. For a cooling fluidoutlet having a height H of 7.620 millimeters and a width W of 0.203millimeters this corresponds to a flow of cooling fluid 210 of about 1standard cubic foot/minute (scfm) from each cooling fluid outlet 206.

The flow of cooling fluid 210 emitted from each cooling tube 202, 204 isdirected across the optical fiber pathway 208 and, more specifically,across the optical fiber 300, towards the opposing cooling tube therebycooling the optical fiber. After the flow of cooling fluid 210 traversesthe optical fiber pathway 208, the cooling fluid is vented to theambient atmosphere around the opposing cooling tube and/or in adirection perpendicular to the draw direction (e.g., the directionindicated by arrow 250 in FIG. 7). For example, FIG. 2 graphicallyillustrates a fluid flow egress 212 in a direction which isperpendicular to the draw direction of the optical fiber. Because thecooling fluid is vented out of the optical fiber cooling system 200 a ina direction perpendicular to the axial length of the optical fibercooling system, bulk axial flow of the cooling fluid is preventedthereby improving the cooling capabilities of the optical fiber coolingsystem 200 a.

Referring now to FIGS. 8 and 9, an alternative embodiment of an opticalfiber cooling system 200 b is depicted. FIG. 8 depicts a horizontalcross section of the optical fiber cooling system. In this embodimentthe optical fiber cooling system 200 b comprises a cooling tube 402, acooling fluid supply plenum 408 and at least one cooling fluid exhaustplenum. In the the embodiment shown in FIG. 8 the optical fiber coolingsystem 200 b comprises a first cooling fluid exhaust plenum 404 and asecond cooling fluid exhaust plenum 406.

The cooling tube 402 is generally circular in cross section.Accordingly, in the embodiment shown herein, the cooling tube 402 issubstantially cylindrical. The cooling tube 402 is open at either endthereby forming an optical fiber pathway 414 through the cooling tube402 through which an optical fiber 300 may be drawn. In the embodimentshown in FIG. 8, the cooling tube 402 is formed from a metallicmaterial, such as an aluminum or steel alloy, or from polymericmaterials, composite materials or ceramics. The cooling tube generallyhas a wall thickness of less than about 13.0 millimeters, morepreferably less than about 6.5 millimeters and, most preferably, lessthan about 3.5 millimeters. Further, the inner diameter of the coolingtube 402 is preferably less than about 100 mm and, more preferably, lessthan or equal to 50 mm. In the embodiments described herein the coolingtube 402 has an axial length of less than about 6 meters, morepreferably less than about 5 meters and, most preferably, about 4meters. However, it should be understood that the axial length of thecooling tube may be longer than 6 meters or shorter than 4 metersdepending on the specific system in which the cooling tubes areemployed.

To facilitate cooling an optical fiber 300 positioned in the coolingtube 402, the cooling tube comprises a plurality of cooling fluid inlets410 disposed along the axial length of the cooling tube 402. Forexample, the cooling fluid inlets 410 may be equidistantly spaced alongthe axial length of the cooling tube 402, as described hereinabove withrespect to the cooling fluid outlets of the embodiment of the coolingtubes shown in FIGS. 2-7. Alternatively, the cooling fluid inlets may bepositioned in groups and the groups may be equidistantly spaced alongthe axial length of the cooling tube 402. However, in the embodiment ofthe cooling tube 402 shown in FIG. 8, the cooling fluid inlets aregenerally configured to direct a flow of cooling fluid across theoptical fiber pathway from at least two different directions. In oneembodiment, the cooling fluid inlets may be positioned on opposite sidesof the cooling tube 402. For example, where individual cooling fluidinlets 410 are equidistantly spaced along the axially length of thecooling tube 402, axially consecutive cooling fluid inlets 410 may beoffset in a circumferential direction such that the cooling fluid inlets410 are 180 degrees apart. Accordingly, in this embodiment, it should beunderstood that axially consecutive cooling fluid inlets 410 are notdirectly opposed to one another (i.e., axially consecutive cooling fluidinlets are not located at opposite ends of a diameter of the coolingtube 402). Alternatively, when the cooling tube 402). Alternatively,when the cooling fluid inlets 410 are positioned in groups, axiallyconsecutive cooling fluid inlets in a single group may be positioned onthe same side of the cooling tube 402 while axially consecutive groupsof cooling fluid inlets are offset in the circumferential direction by180 degrees. However, it should be understood that the circumferentialoffset between axially consecutive cooling fluid inlets or axiallyconsecutive groups of cooling fluid inlets may be other than 180degrees. For example, in one embodiment, axially consecutive coolingfluid inlets or groups of cooling fluid inlets may be offset in thecircumferential direction by about 120 degrees. Accordingly, it shouldbe understood that the cooling fluid inlets 410 are positioned such thata flow of cooling fluid is directed substantially across the diameter ofthe cooling tube 402 in at least two different directions.

In this embodiment, the cooling fluid inlets 410 may have a height andwidth similar to the height and width of the cooling fluid outletsdescribed above and depicted in FIG. 5. Further, in one embodiment, thesidewalls of the cooling fluid inlets may be substantially parallelthrough the thickness of the cooling tube similar to the cooling fluidoutlets described above and shown in FIG. 4A. Alternatively, thesidewalls of the cooling fluid inlets 410 may be tapered from the outerdiameter to the inner diameter of the cooling tube 402.

For example, as depicted in FIG. 9, the sidewalls 430, 432 of thecooling fluid inlet 410 are tapered from the outer diameter of thecooling tube to the inner diameter of the cooling tube. Morespecifically, in the embodiment of the cooling tube 402 shown in FIG. 9,the sidewalls of the cooling fluid inlet 410 taper from the outerdiameter of the cooling tube 402 to the inner diameter of the coolingtube 402 with respect to the centerline 433 of the cooling fluid inlet410. In the embodiments shown and describe herein, the sidewalls 430,432 are each oriented at an angle 13 with respect to the centerline 433of the cooling fluid inlet 410. The angle 13 may be from about 12.5degrees to about 25 degrees and, more preferably, from about 13.0degrees to about 21 degrees. Accordingly, it should be understood that,in the embodiment shown in FIG. 9, the cooling fluid inlet 410 tapers tothe height H at the inner diameter and as such, the height of thecooling fluid inlet at the outer diameter of the cooling tube is greaterthan the height H at the inner diameter. In one embodiment, thesidewalls of the cooling fluid inlet may be tapered such that a flow ofcooling fluid 210 passing through the cooling fluid inlet is focused atthe center of the cooling tube 402. In another embodiment, the sidewallsof the cooling fluid inlet may be tapered such that a flow of coolingfluid 210 passing through the cooling fluid inlet is not through thecooling fluid inlet is not focused at the center of the cooling tube402, such as when the flow of cooling fluid is focused between thecooling fluid inlet at the center or when the flow of cooling fluid isfocused between the center and the opposing wall of the cooling tube402.

In order to prevent the bulk axial flow of cooling fluid through thecooling tube 402, the cooling tube 402 may comprise a at least onecooling fluid vent 412 positioned along the axial length of the coolingtube 402 between first and second ends of the cooling tube. In theembodiment shown in FIG. 8 the cooling tube 402 comprises a plurality ofcooling fluid vents 412. The cooling fluid vents generally have a crosssectional area which is larger than the cross sectional area of acooling fluid inlet. In the embodiments shown in FIG. 8, the coolingfluid vents are offset from the cooling fluid inlets 410 in acircumferential direction. Accordingly, it should be understood that thecooling fluid vents 412 are not opposed to the cooling fluid inlets 410.For example, in the embodiment shown in FIG. 8, the cooling fluid vents412 are offset at about a 90 degree angle with respect to the coolingfluid inlets 410. However, it should be understood that various otherrelative orientations between the cooling fluid vents 412 and thecooling fluid inlets 410 may be possible. The cooling fluid vents 412offset form the cooling fluid inlets 410 in the circumferentialdirection facilitates coupling the cooling fluid vents 412 to acontinuous exhaust plenum, as will be described in more detail herein.Further, while the embodiment in FIG. 8 shows the cooling fluid vents412 as directly opposed to one another, it should be understood that, inother embodiments, the cooling fluid vents may be offset from oneanother in the axial direction of the cooling tube such that axiallyconsecutive cooling fluid vents are not in direct opposition to oneanother (i.e., axially consecutive cooling fluid vents are notpositioned at opposite ends of a diameter of the cooling tube 402). Inone embodiment, the cooling fluid vents 412 comprise slots which extendsubstantially along the entire axial length of the cooling tube 402. Inanother embodiment, the cooling fluid vents are discrete openings in thecooling tube 402.

Still referring to FIGS. 8 and 9, the cooling fluid vents 412 may befluidly coupled to a first cooling fluid exhaust plenum 404 and a secondcooling fluid exhaust plenum 406. The cooling fluid exhaust plenums 404,406 may extend along the axial length of the cooling tube 402. In oneembodiment, the cooling fluid exhaust plenums 404, 406 and the coolingtube 402 are integrally formed such as when the cooling fluid exhaustplenums and the cooling tube are formed in a single extrusion operation.Alternatively, the cooling fluid exhaust plenums 404, 406 may be formedseparately from the cooling tube 402 and attached to the cooling tubesuch as by welding and/or conventional fasteners. While the embodimentof the optical fiber cooling system 200 b illustrated in FIG. 8 depictsa single exhaust plenum attached to either side of cooling tube 402, itshould be understood that, when the optical fiber cooling system 200 bcomprises multiple discrete cooling fluid vents positioned along theaxial length of the cooling tube 402, each cooling fluid vent may befluidly coupled to a separate exhaust plenum.

In one embodiment, the cooling fluid exhaust plenums 404, 406 may beopen to the ambient atmosphere thereby allowing cooling fluid to vent tothe atmosphere. In another embodiment, the cooling fluid exhaust plenums404, 406 may be fluidly coupled to a fluid recovery system (not shown).The fluid recovery system may be used to actively exhaust the coolingfluid exhaust plenums 404, 406 by applying a negative pressure on thecooling fluid exhaust plenums 404, 406 thereby drawing the cooling fluidout of the optical fiber cooling system 200 b. To facilitate use of thefluid recovery system, one end of each cooling fluid exhaust plenum 404,406 may be closed and the opposite end may be coupled to the fluidrecovery system. Alternatively, both ends of each cooling fluid exhaustplenum 404, 406 may be fluidly coupled to the fluid recovery system.

In order to provide a flow of cooling fluid through the cooling fluidinlets 410 and across the optical fiber pathway 414, the cooling tube402 is positioned in and substantially coaxial with a cooling fluidsupply plenum 408. Accordingly, it should be understood that the coolingtube 402 is substantially centered in the cooling fluid supply plenum408 and operable to supply cooling fluid to the cooling fluid inletspositioned about the circumference of the cooling fluid tube 402.Further, it should be understood that the cooling fluid exhaust plenums404, 406 are also located in the cooling fluid supply plenum 408. Thecooling fluid supply plenum 408 may generally be a tube or similarstructure formed from a metallic material, polymers, ceramics and/orcomposite materials. In the embodiment of the cooling fluid supplyplenum 408 shown herein, the cooling fluid supply plenum 408 is formedfrom a metallic material such as an aluminum alloy or a steel alloy.

In general, both ends of the cooling fluid supply plenum 408 are sealedbetween the inner diameter of the cooling fluid supply plenum 408 andthe outer diameter of the cooling tube 402 and between the innerdiameter of the cooling fluid supply plenum and the outer diameter ofthe cooling fluid exhaust plenums 404, 406 such that the space betweenthe cooling tube 402 and the cooling fluid supply plenum 408 and thespace between the cooling fluid exhaust plenums fluid exhaust plenums404, 406 and the cooling fluid supply plenum may be filled with apressurized cooling fluid which, in turn, is released into the coolingtube 402 through the cooling fluid inlets 410.

The cooling fluid supply plenum 408 may be fluidly coupled to a coolingfluid supply system (not shown). In one embodiment, the cooling fluidsupply system may comprise a compressor or other apparatus for supplyinga flow of pressurized cooling fluid. In another embodiment, the coolingfluid supply system may comprise a fan or other mechanism for directinga flow of cooling fluid into the cooling fluid supply plenum 408.

Referring to FIG. 8, an optical fiber 300 drawn through the cooling tube402 along the optical fiber pathway 414. As the optical fiber 300 isdrawn over the optical fiber pathway 414, cooling fluid is supplied tothe optical fiber cooling tubes 402 via the cooling fluid inlets 410.The cooling fluid may comprise an elemental gas, such as helium ornitrogen, or a mixture of gasses such as, for example, air.Alternatively, the cooling fluid may comprises a combination of variousgasses such as helium, nitrogen and/or carbon dioxide. The cooling fluidmay be chilled or, alternatively, supplied to the optical fiber coolingsystem 200 b at ambient temperatures.

In one embodiment, the cooling fluid may be supplied to the coolingfluid supply plenum and, thereafter, to the cooling tube 402 atpressures suitable for achieving a flow of cooling fluid 210 from eachcooling fluid inlet 412 having a velocity of less than about 0.95 mach.For example, when the cooling fluid is air, the air may be supplied tothe cooling fluid supply plenum such that the pressure in the coolingfluid plenum is about 7 psig. For a cooling fluid inlet having a heightH of 7.620 millimeters and a width W of 0.203 millimeters thiscorresponds to a flow of cooling fluid of about 1 standard cubicfoot/minute (scfm) from each cooling fluid inlet.

The flow of cooling fluid 210 emitted from each cooling fluid inlet 410is directed across the optical fiber pathway 414 and, more specifically,across the optical fiber 300, towards the opposite side of the coolingtube thereby cooling the optical fiber. After the flow of cooling fluid210 traverses the optical fiber pathway 414, the cooling fluid is ventedthrough the cooling fluid vents 412 in a direction substantiallyperpendicular to the direction of travel of the optical fiber and intothe cooling fluid exhaust plenums 404, 406.

For example, FIG. 8 graphically illustrates a fluid flow egress 412 in adirection which is perpendicular to the draw direction of the opticalfiber. Because the cooling fluid is vented out of the cooling tube 402in a direction perpendicular to the axial length of the cooling tubeover the axial length of the cooling tube 402, bulk axial flow of thecooling fluid is prevented thereby improving the cooling capabilities ofthe optical fiber cooling system 200 b. After the cooling fluid isvented into the cooling fluid exhaust plenums 404, 406, the coolingfluid may be further vented to the ambient atmosphere or, alternatively,recovered with a fluid recovery system.

In either embodiment of the cooling fluid systems shown and describedherein, the optical fiber cooling system has sufficient cooling capacityto cool the optical fiber 300 such that, as the optical fiber 300 exitsthe optical fiber cooling system 200 a, 200 b, the optical fiber 300 isgenerally at a temperature at which a protective coating may be appliedto the optical fiber 300. For example, in the embodiments describedherein, the optical fiber has a temperature of less than about 80° C.upon exiting the optical fiber cooling system 200 a, 200 b.

Referring again to FIG. 1, after the optical fiber 300 exits the opticalfiber cooling system 200, the optical fiber enters a coating system 130in which one or more protective coatings are applied to the opticalfiber and cured. The coating(s) may comprise polymeric coating such as,for example, a UV curable coating or a thermoplastic coating. However,it should be understood that the coating system may be configured toapply any type of material suitable for coating an optical fiber andthereby enhancing the optical properties of the optical fiber 300 and/orfor protecting the optical fiber 300.

As the optical fiber 300 exits the coating system 130, the diameter ofthe coated optical fiber 300 is measured again using a non-contactsensor 118. Thereafter, a non-contact flaw detector 132 is used toexamine the coated optical fiber 300 for damage and/or flaws that mayhave occurred during the manufacture of the optical fiber 300. It shouldbe understood that, after the optical fiber 300 has been coated, theoptical fiber 300 is less susceptible to damage due to mechanicalcontact. Accordingly, in subsequent processing stages (not shown)mechanical contact with the optical fiber 300 may be acceptable.

As shown in FIG. 1, a fiber take-up mechanism 140 utilizes variousdrawing mechanisms 142 and pulleys 141 to provide the necessary tensionto the optical fiber 300 as the optical fiber is drawn through thesystem 100. Accordingly, it will be understood that the fiber take-upmechanism 140 controls the speed at which the optical fiber 300 is drawnthrough the through the system 100. After manufacture of the opticalfiber 300 is complete, the optical fiber 300 is wound onto a storagespool 148.

It should now be understood that the optical fiber cooling systemsdescribed herein may be incorporated in systems for manufacturing coatedoptical fiber to facilitate cooling the optical fiber before a coatingis applied to the optical fiber. Further, it will be understood that theoptical fiber cooling systems described herein facilitate faster opticalfiber draw speeds (e.g., draw speeds up to or in excess of 35 m/s) dueto the improved cooling capabilities of the optical fiber cooling systemwhich, in turn, are due to the substantial mitigation or elimination ofbulk axial flow of cooling fluid through the optical fiber coolingsystem.

Further, by positioning the cooling fluid outlets (or cooling fluidinlets, depending on the configuration of the optical fiber coolingsystem) such that axially consecutive cooling fluid outlets aregenerally in 180 degree opposition with one another (albeit offset fromone another in the axial direction of the optical fiber cooling system)improves the dynamic stability of the optical fiber as it passes throughthe optical fiber cooling system. This improved dynamic stability, inturn, facilitates the use of higher cooling fluid flow rates andtherefore improves the cooling capacity of the optical fiber coolingsystem.

The elimination of bulk axial flow and the use of higher cooling fluidflow rates significantly improve the cooling capabilities of the opticalfiber cooling systems described herein such that less expensive coolingfluids may be used in conjunction with the optical fiber coolingsystems. For example, instead of chilled helium, a less expensive gassuch as nitrogen or air may be used with the optical fiber coolingsystems. When used in conjunction with the systems descried herein theseless expensive gasses still provide for improved cooling capabilitiesand further decrease optical fiber production costs. Further, theoverall improvement in the cooling capabilities of the optical fibercooling systems may also facilitate eliminating the need for chillingthe cooling fluid thereby further reducing the costs associated withoptical fiber manufacturing.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

1. An optical fiber cooling system comprising a first cooling tube oriented substantially in parallel with and spaced apart from a second cooling tube with an optical fiber pathway positioned between the first cooling tube and the second cooling tube, wherein: the first cooling tube comprises a plurality of cooling fluid outlets positioned along an axial length of the first cooling tube, wherein the cooling fluid outlets of the first cooling tube are oriented to direct a flow of cooling fluid across the optical fiber pathway towards the second cooling tube; and the second cooling tube comprises a plurality of cooling fluid outlets positioned along an axial length of the second cooling tube, wherein the cooling fluid outlets of the second cooling tube are oriented to direct a flow of cooling fluid across the optical fiber pathway towards the first cooling tube.
 2. The optical fiber cooling system of claim 1 wherein the cooling fluid outlets of the first cooling tube are offset from the cooling fluid outlets of the second cooling tube in an axial direction such that the cooling fluid outlets of the first cooling tube are not opposed to the cooling fluid outlets of the second cooling tube.
 3. The optical fiber cooling system of claim 1 wherein: axially consecutive cooling fluid outlets on the first cooling tube are equidistantly spaced along the axial length of the first cooling tube; and axially consecutive cooling fluid outlets on the second cooling tube are equidistantly spaced along the axial length of the second cooling tube.
 4. The optical fiber cooling system of claim 1 wherein: the cooling fluid outlets of the first cooling tube are positioned along the axial length of the first cooling tube in groups and consecutive groups of cooling fluid outlets are equidistantly spaced along the axial length of the first cooling tube; and the cooling fluid outlets of the second cooling tube are positioned along the axial length of the second cooling tube in groups and consecutive groups of cooling fluid outlets are equidistantly spaced along the axial length of the second cooling tube.
 5. The optical fiber cooling system of claim 1 wherein the optical fiber pathway is not enclosed such that the optical fiber pathway is exposed to ambient temperature, pressure and atmosphere.
 6. The optical fiber cooling system of claim 1 further comprising a fluid containment enclosure, wherein the first cooling tube and the second cooling tube are disposed in the fluid containment enclosure.
 7. The optical fiber cooling system of claim 6 further comprising a cooling fluid recovery system fluidly coupled to the fluid containment enclosure.
 8. The optical fiber cooling system of claim 1 further comprising a cooling fluid supply fluidly coupled to the first cooling tube and the second cooling tube.
 9. The optical fiber cooling system of claim 1 wherein the cooling fluid outlets are tapered from an inner diameter of the cooling tube to an outer diameter of the cooling tube.
 10. The optical fiber cooling system of claim 1 wherein the cooling fluid outlets have a width of less than about 0.5 mm and a height of greater than about 2.5 mm at an outer diameter of the cooling tube. 11-20. (canceled) 